Filaminast (WAY-PDA 641[1]) was a drug candidate developed by Wyeth-Ayerst.[2]:Table 2 It was a phosphodiesterase 4 inhibitor (PDE4 inhibitor) and an analog of rolipram, which served as a prototype molecule for several development efforts.[3][4]:668, 678 It was discontinued after a Phase II trial showed that its therapeutic window was too narrow; it could not be dosed high enough without causing significant side effects (nausea and vomiting), which was a problem with the rolipram class of molecules.[4]:678